Episode 18

Suiryu overwhelms Lightning Max as Genos receives a warning about monsters swarming the city. Sneck outlasts Benpatsu, and though the announcers want to evacuate the crowd once the alerts arrive, Bakuzan talks them out of it. Sour Face bests Jakumen, the two parting as friends, and he rushes to tell Saitama about the win only to find him gone to the restroom. When Saitama finally faces Bakuzan, the villain gloats about how he will annihilate him, but the instant he tugs on Saitama's wig he is comically launched clear of the ring with one punch. Genos wipes out nearly every monster in the area, sparing only the Demon-level Awakened Cockroach, and while his guard is down an unseen attacker strikes him. Hero Association personnel locate Pineapple and Mohican and learn Waganma has been taken, though Narinki has not.

Do-S manages to seize control of every one of Fubuki's followers, yet Fubuki turns them right back. Do-S admits she is targeting Fubuki to bait out Tatsumaki, who, Fubuki warns, senses whenever her sister is harmed. On cue a monster crashes down and Tatsumaki appears, easily hurling the brainwashed underlings into buildings as Do-S flees, then lecturing Fubuki that leaning on subordinates only breeds weakness before departing. In the final tournament bout, Suiryu casually slips past Sneck's blows, needling him for being a purposeless hero chasing strength for its own sake, then dropping him with one strike while remarking that the genuinely strong always endure. The post-credits scene reveals a Dragon-level monster named Gouketsu as the being who felled Genos, shows Sweet Mask's concert overrun, monsters assaulting the hospital sheltering Mumen Rider and Tanktop Master, Nyan seeking Puri-Puri Prisoner who has already broken out to fight, and Gyoro Gyoro and Orochi holding a captured Metal Knight.

Saitama eliminates Bakuzan with a single blow after the wig incident. Genos clears the local monsters but is ambushed and defeated by the hidden Gouketsu, who is confirmed as a Dragon-level foe. Tatsumaki routs Do-S's controlled thralls and warns Fubuki against relying on henchmen. The Monster Association's wider offensive spreads to a concert, a hospital, and the capture of Metal Knight, while Puri-Puri Prisoner leaves confinement to join the fight.

Named The Monster Uprising, this installment bridges the Monster Raid Arc and the Super Fight Arc, drawing on chapters 60 and 62 through 66 plus the Star omake. Japan saw it on May 14, 2019, and the English airing came November 16, 2019, carrying Seijaku no Apostle as its opening and Chizu ga Nakute mo Modoru Kara as its ending. The anime abbreviates Sneck's duel with Benpatsu, thins out Genos's monster count, and gives him a High Voltage Fist finisher against Face Ripper in place of the manga's incineration kill.